Three-Dimensional Structural Analysis of Ferromanganese Nodules from the Western North Pacific Ocean Using X-ray Computed Tomography

The three-dimensional layered growth structure of 934 ferromanganese nodule samples collected from dives in the Pacific Ocean around Minamitorishima Island was assessed using X-ray computed tomography (X-ray CT) to elucidate their growth history. The thickness of the layered structure measured in three orthogonal directions showed that the ferromanganese nodules grew equally in all directions regardless of shape and size. Based on differences in CT numbers, a layered structure was subdivided into sublayers I, II, III, and IV, which corresponded to petrological features. The nodules were then classified as Types I, II, III, and IV according to whether they had sublayers I, I and II, I–III, or I–IV, respectively. Correlations between the total thickness of the layers and the number of sublayers indicated that both represented the relative age of the nodules. Nodules with all these types were recovered from most of the sampling sites, and histograms of the total layer thickness at each dive site showed several peaks. These findings indicated that the initiation of nodule growth was intermittent, rather than simultaneous. Three distinct thickness peaks were found at many sites throughout the study area, suggesting that at least three nodule initiation events covering hundreds of kilometers initiated the growth of ferromanganese nodules.

In situ imaging of two-dimensional surface growth reveals the prevalence and role of defects in zeolite crystallization

Zeolite crystallization predominantly occurs by nonclassical pathways involving the attachment of complex (alumino)silicate precursors to crystal surfaces, yet recurrent images of fully crystalline materials with layered surfaces are evidence of classical growth by molecule attachment. Here we use in situ atomic force microscopy to monitor three distinct mechanisms of two-dimensional (2D) growth of zeolite A where we show that layer nucleation from surface defects is the most common pathway. Direct observation of defects was made possible by the identification of conditions promoting layered growth, which correlates to the use of sodium as an inorganic structure-directing agent, whereas its replacement with an organic results in a nonclassical mode of growth that obscures 2D layers and markedly slows the rate of crystallization. In situ measurements of layered growth reveal that undissolved silica nanoparticles in the synthesis medium can incorporate into advancing steps on crystal surfaces to generate defects (i.e., amorphous silica occlusions) that largely go undetected in literature. Nanoparticle occlusion in natural and synthetic crystals is a topic of wide-ranging interest owing to its relevance in fields spanning from biomineralization to the rational design of functional nanocomposites. In this study, we provide unprecedented insight into zeolite surface growth by molecule addition through time-resolved microscopy that directly captures the occlusion of silica nanoparticles and highlights the prevalent role of defects in zeolite crystallization.

Flexible and conductive cellulose substrate by layered growth of silver nanowires and indium-doped tin oxide

Regenerated cellulose film (RCF) has potential as a conductive substrate due to features such as its degradability, transparency, and flexibility. Indium doped tin oxide (ITO) is a conventional conductive material, but its rigidity restricts the formation of flexible conductive film. In this study, silver nanowires (AgNWs) were introduced between the RCF and the ITO conductive framework. Additionally, the fabrication of flexible, conductive, and transparent RCF was conducted. The AgNWs-ITO based RCF demonstrated high conductivity (170 Ω per sq) and transparency (78%) by the addition of 50 μL of AgNWs. After bending the sample 50 times with a 5 mm curve radius, the as-prepared conductive RCF presented an electric resistance improvement of 19%, with a 485% increase for the control ITO-based RCF. This is a result of the AgNWs framework, which can lessen the destruction of the bending treatment on the conductive layer and can also desirably connect the ITO conductive sections. The novel approach can expedite the versatile applications of flexibly conductive RCF on printable, portable, and wearable electronic devices.

Structure and formation mechanisms of (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 particles under hydrothermal conditions

(K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 powders were synthesized via hydrothermal method. The effects of different reaction conditions on crystal structure, micro-morphology and phase formation were analysed by XRD and SEM in detail. The results reveal that (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 powders with orthorhombic lattice structure are synthesized at 200?C for 18 h with the total initial alkali concentration of 8mol/l. The average particle size of synthesized powders is about 500-700 nm, which has regular cubic morphology with uniform distribution. Moreover, doping with La3+ and Sb5+ inhibits the crystal growth. The phase evolution of the powders revealed that the hydrothermal synthesis of (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 underwent two steps, where an intermediate product of K4Na4Nb6O19? 9H2O was found in the early stage at 140?C. Based on the results, the formation mechanism of (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 powders was proposed. It can be inferred that the crystal growth model of (K0.46Na0.46La0.08)(Nb0.94Sb0.06)O3 is dissolution-crystal growth-recrystallization with the characteristics of layered growth.